Polybutylene terephthalate (PBT) resins are semicrystalline thermoplastics used in a variety of durable goods. PBT resins are now widely used for components in the electronics and automotive industries. As these market sectors continue to expand and evolve, demand for PBT has continued to grow. Thus, in 2009, worldwide consumption of PBT was reported to total 750 kilotons. Demand for PBT is projected to increase at least 5 percent per year, leading to a projected demand of 1300 kilotons by the year 2020.
PBT producers continue to face the challenge of meeting increasing demand for PBT while dealing with higher production costs. One approach to improving process yield and reducing cost on an industrial scale relates to using PBT oligomer to make PBT resins. PBT oligomer can be prepared from PTA and BDO. To be useful in making PBT resin for specific end purposes, it is necessary to strictly control the CEG and IV values of the PBT oligomer. There is thus an ongoing need for processes for making PBT resins from PBT oligomer with desired IV and CEG values.